Relay flip-flop



J. N. PEARSE 3,370,206

RELAY FLIP-FLOP Feb. 20, 1968 Filed May 26, 1965- .INVENTOR- JAMES N- PEARSE United States Patent 0 3,370,206 RELAY FLIP-FLOP James N. Pearse, Menomonee Falls, Wis., assignor to Allen-Bradley Company, Milwaukee, Wis., a corporation of Wisconsin Filed May '26, 1965, Ser. No. 458,983 4 Claims. (Cl. 317-140) ABSTRACT OF THE DISCLOSURE The reed relay flip-flops employ two relays, each having a pair of common connected coils to actuate its contacts. The first embodiment has the input signal alternately delivered to the energizing coil of the leading relay through a resistor, and to the deenergizing coil through the con tacts of the trailing relay, or to the deenergizing coil of the trailing relay through a resistor and to the energizing coil through the contact of the leading relay. In the other embodiment, the input signal is alternately fed to the common contact of each relay, the stationary contacts of each relay being connected to the coils of the other relay.

The present invention pertains to a relay flip-flop utilizing two relays, each of which has an energizing coil, a deenergizing coil and contacts operated by the coil; one of the relays having its deenergizing coil connected to be energized through the contacts of the other relay, which has its energizing coil connected to be energized through the contacts of the first mentioned relay.

The present invention differentiates from a large portion of the prior art pertaining to flip-flops in that the present invention is a relay flip-flop, as distinguished from electronic flip-flops. The invention is further distinguished from all of the prior art in the extreme austerity of its circuitry. Finally, the present invention is characterized by its inherent ability to operate either as a leading edge or trailing edge device.

As a result of the above described structural characteristics, the present invention achieves a number of objects and unexpected advantages, all of which can be importantly beneficial in a great many flip-flop applications. The use of latched relays provides a memory which will survive power failures, and it can provide an immediately usable output signal requiring no amplification or other modification or transmutation. The austerity of its circuitry, requiring only relays and resistors, greatly reduces the potential for outage or malfunction of any sort, and by virtue of its use of the two most stable and reliable electrical components known, it is highly reliable and stable. Of course, the circuit austerity may also greatly re- .duce the cost for any given level of performance. Finally,

its inherent ability to operate as either leading edge or trailing edge logic module permits its use, with equal facility, as a component both in devices which utilize a clocking signal and those in which no clocking signal is avail- -able.

3,370,266 Patented Feb. 20, 1968 described by reference to the drawings attached, which form a part of the disclosure. The purpose of this disclosure is to describe the invention as well as the manner and process of making and using it in such full, clear, concise, and exact terms as will enable any person skilled in the art to which it pertains, or with which it is most clearly connected, to make and use the same and further its purpose is to set forth the best mode contemplated by the inventor of carrying out the invention. However, this disclosure is not to be confused with the invention itself, for it will be apparent to one skilled in the art how these embodiments may be varied and embellished without departing from the subject matter of the invention. Instead, the subject matter which is regarded as the invention is particularly pointed out and distinctly set forth in the claims which appear at the conclusion of the specification.

In the drawings:

FIG. 1 is a schematic diagram of a second embodiment of the present invention in which resistors are substituted for some of the relay contacts;

FIG. 2 is a schematic diagram of one embodiment of the present invention utilizing only relays in its circuitry.

Referring now specifically to the drawings, in FIG. 1 a relay flip-flop embodying the present invention is diagramed utilizing a combination of relay contacts and resistors as its controlling components. This flip-flop contains a first relay 1, or leading edge relay 1, and a second relay 2, or trailing edge relay 2, each of which has two operating coils. The leading edge relay 1 has a deenergizing coil 3 shown at the top and an energizing coil 4 shown at the bottom, and it is latched by a permanent latching magnet 5. Two sets of contacts 6 and 7 are shown in the first relay 1. The control contacts 6 are involved in the operation of the flip-flop itself, and the leading edge output contact 7 can provide a leading edge output if desired. The deenergizing coil 3 and the energizing coil 4 have their signal return ends connected to a common ground 8. Whereas the deenergizing coil 3 has a reset input terminal 9 connected to its input side to receive a reset signal, the energizing coil 4 has a set input terminal 10 connected to its input side to receive a set signal.

The second, or trailing edge relay 2 is practically identical to the first, or leading edge relay 1. The trailing edge relay 2 also has a deenergizing coil 11 and an energizing coil 12, which have their. signal return ends connected to the common ground 8. The trailing edge relay 2 is also a latched relay utilizing a permanent latching magnet 13. Finally, like the leading edge, or first relay 1, the trailing edge relay 2 is shown to have a set of control contacts 14, which are involved in the operation of the flip-flop,

and a set of trailing edge output contacts 15, which can provide a trailing edge output signal where that is desired. Since the relays 1 and 2 are latched relays, they may be considered as bistable devices in that their contacts 5, 6 and 14, 15, respectively, are normally open and adapted to be latched in the closed position. The polarity dot convention is utilized in the diagram to differentiate between the deenergizing coils 3 and 11 and the energizing coils 4 and 12. The polarity dot convention as employed here means that a positive signal entering a coil on the side adjacent the polarity dot will energize the relay, whereas a positive signal entering a coil from the side opposite to that of the polarity dot will deenergize the relay. Hence, what is termed here as the deenergizing coils 3 and 11 are merely coils connected to receive a positive input signal from the side opposite the polarity dot, and the energizing coils 4 and 12 are relay coils connected to receive the positive input signal at the side adjacent the polarity dot. While the relays are shown to have only two sets of contacts, that showing is diagrammatic only and any number of output signals can be provided by the relays 1 and 2 shown by the addition of more output contacts.

In physical structure the relays utilized here are reed relays. Each set of contacts is comprised of a pair of resilient conductive reeds mounted in opposite ends of a glass envelope so that their free ends project into the cavity of the envelope and overlap each other in close proximity, while their opposite ends project outward from the ends of the envelope to serve as terminals which can be connected to the wires of an electrical circuit. The coils 3, 4 and 11, 12 are then wound around the glass envelope or envelopes and the permanent latching magnets 5 and 13 are placed adjacent to the overlapping free end of the reed but outside of the envelope.

A complement input signal terminal 16, which is adapted to receive a unidirectional input signal from a source that is not shown, is connected to a common moving contact 17 of an input switch that has one stationary contact 18 connected through a current limiting resistor 19 to the input side of the energizing coil 4 of the leading edge relay 1, and the same stationary contact 18 is also connected to one side of the control contacts 14 of the trailing edge relay 2. The other side of the control contact 14 of the trailing edge relay 2 is connected to the input side of the deenergizing coil 3 of the leading edge relay 1. A second stationary contact of the input switch is connected through a second current limiting resistor 21 to the input side of the deenergizing coil 11 of the trailing edge relay 2 and it is also connected to the control contact 6 of the leading edge relay 1. The other side of the control contact 6 of the leading edge relay 1 is connected to the input side of the energizing coil 12 of the trailing edge relay 2.

In the operation of the first embodiment shown in FIG. 1, assume that a constant unidirectional input signal is applied to the complement input signal terminal 16. With the common moving contact 17 of the input switch in the position shown in the drawing, the input signal will energize the leading edge relay 1 as it passes through the current limiting resistor 19 and the energizing coil 4. When the leading edge relay 1 is energized, the contacts 6 and 7 will be closed, and no further action occurs.

When the common moving contact 17 is moved over to the second or left hand stationary contact 20, the input signal through the current limiting resistor 21 and the deenergizing coil 11 of the trailing edge relay 2 will have no effect on the condition of the relay 2. However, the input signal passing through the closed control contacts 6 of the leading edge relay 1 will energize the energizing coil 12 of the trailing edge relay 2. Since the current limiting resistor 21 reduces the current to the deenergizing coil 11 relative to the energizing coil 12, the flux gener ated in the energizing coil 12 is sufiicient to overcome the deenergizing effect of the flux from the deenergizing coil 11. Therefore, the trailing edge relay 2'will be energized, closing its control contact 14 and its trailing edge output contact 15. No further action will occur until the moving contact 17 is moved back to the right hand or first stationary contact 18 when it will have the effect of deenergizing the leading edge relay 1.

The embodiment shown in FIG. 2, like that in FIG. 1, employs a trailing edge relay 22 and a leading edge relay 23. The relays 22 and 23 are latched reed relays utilizing permanent latching magnets 24 and 34. The trailing edge relay 22 has a deenergizing coil 25, an energizing coil 26, which actuate a set of output contacts 27 and a set of break-before-make control contacts 28. In practice the control contacts 28 may be made up of two sets of reed contacts connected together according to well known techniques. The deenergizing coil and the energizing coil 26 have their signal return ends connected to a common ground 29, and the input ends are connected in a manner to be described below.

The leading edge relay 23 has the same structure as the trailing edge relay 22 described above. The leading edge relay 23 has an energizing coil 30 and a deenergizing coil 31 arranged to actuate a set of output contacts 32 and a set of control contacts 33, the contacts 31, 32 and 33 being latched by permanent latching magnet 34. The input end of the energizing coil 30 is connected to a set input signal terminal 35 and the input end of the deenergizing coil 31 is connected to -a reset input signal terminal 36.

A complement input signal terminal 37 is connected to the common moving contact 38 of an input switch that has one fixed contact 39 connected to the common contact 40 of the control contact 28 and the trailing edge relay 22 and another fixed contact 41 connected to a common contact 42 of the control contacts 33 in the leading edge relay 23. The contact contacts 28 of the trailing edge relay 22 has its stationary contacts 43 and 44 respectively connected to the input ends of the energizing coil 30 and the deenergizing coil 31 of the leading edge relay 23. Similarly, the control contacts 33 of the leading edge relay 23 include stationary contacts 45 and 46 connected respectively to the input ends of the deenergizing coil 25 and the energizing coil 26 of the trailing edge relay 22.

In operation, assume that a constant unidirectional current is applied to the complementary input signal terminal 37. In the shown position of the common moving contacts 38 of the input signal switch, the input signal will pass through the control contact 33 of the leading edge relay 23 entering the deenergizing coil 25 of the trailing edge relay 22, which would have no effect uopn the condition of the trailing edge relay 22. When the moving contact 38 of the input signal switch is moved over to the left hand fixed contact 39 of the input signal switch the input signal passes through the control contact 28 of the trailing edge relay 22 and energizes the energizing coil 30 of the leading edge relay 23 to energize it. When the moving contact 38 of the input signal switch is moved back to the right hand stationary contact 41 of the input switch the input signal will now pass through the moving contact 42 of the energized leading edge relay 23, passing through the fixed contact 46 of the control contact 33 and entering the energizing coil 26 of the trailing relay 22, to energize it. When the common moving contact 38 of the input signal switch is shifted back again to the left hand stationary contact 39 of that switch the input signal will then pass through the energized control contacts 28 of the trailing edge relay 22. to deenergize the leading edge relay 23 by passing through the deenergizing coil 31 of that relay 23. Finally, when the moving contact 38 of the input signal switch is moved back to the right hand stationary contact 41 of that switch the input signal will pass through the control contact 33 of the leading edge relay 23 to energize the deenergizing coil 25 of the trailing edge relay 22, thus deenergizing the latter and restoring the flip-flop to its original condition as shown in the drawing.

Output signals can be taken from either of the output signal contacts 7 and 15 in the embodiment shown in FIG. 1 and 27 and 32 in the embodiment shown in FIG. 2. By selecting the output contacts of either the trailing edge relay 2 or 23 or the leading edge relay 1 or 22, trailing edge or leading edge logic operation can be obtained. Each of the embodiments of the flip-flop shown can be set by imposing an input signal upon the set terminal 10 or 35 or, if the flip-flop is in a set condition it can be reset by imposing an input signal on the appropriate reset terminal 9 or 36.

In spite of the paucity of components in these embodiments of the present invention, there is room for variations within the scope of the invention. For example, other latching means, such as a coil, could be substituted for the permanent magnets 5, 13, 24 and 34. Nor is the invention confined to reed relays. Various equivalent contact structures are known and could be substituted for those shown.

It is readily apparent from the foregoing disclosure that flip-flops embodying the present invention can achieve virtually prefect circuit austerity while utilizing the most stable and reliable electrical components known. The advantages to be derived from such structure have been mentioned above and it remains only to define the subject matter of the invention, and as such I claim:

1. A relay flip-flop comprising the combination of a first relay having an energizing coil, a deenergizing coil, contact means actuated by said coils, and a current limiting resistor connected in series with said energizing coil;

a second relay having an energizing coil, a deenergizing coil, contact means actuated by said coils, and a current limiting resistor connected in series with said deenergizing coil;

said first relay deenergizing coil connected to receive an input signal through said secondrelay contact means;

said second relay energizing coil being connected to receive an input signal through said first relay contact means;

said second relay deenergizing coil being adapted to receive an input signal through said current limiting resistor simultaneously with said second relay energizing coil said current limiting resistor reducing said input signal to said deenergizing coil'to permit a field simultaneously generated by said input signal to said energizing coil to actuate said contacts;

and said first relay deenergizing coil being adapted to receive an input signal simultaneously with said first relay energizing coil said current limiting resistor in series wtih said energizing coil weakening said input signal to said energizing coil so that said simultaneous input signal to said deenergizing coil actuates said contacts.

2. A relay flip-flop comprising the combination of a first latching relay having an energizing coil, a deenergizing coil, normally open contact means, and a current limiting resistor in series with said energizing coil;

a second latching relay having an energizing coil, a deenergizing coil, normally open contact means, and a current limiting resistor in series with said deenergizing coil;

an input signal switch means adapted to receive an input signal and to alternately complete an input circuit to a first contact and a second contact;

said first relay deenergizing coil being connected through said second relay cont-act means to said first input switch contact, and said second relay energizing coil being connected through said first relay contact means to said second input switch contact;

and said second relay deenergizing coil being connected through said current limiting resistor to said second input switch contact and said first relay energizing coil being connected through said current limiting resistor to said first input switch contact, said current limiting resistor acting to allow a simultaneous input signal to the other coil of the respective relay to control the contact means of that relay.

3. A relay flip-flop as set forth in claim 2 wherein said first relay contains output contacts.

4. A relay flip-flop as set forth in claim 2 wherein said second relay contains output contacts.

References Cited UNITED STATES PATENTS 2,636,932 4/1953 Oberman et al. 3l7-l40 3,025,433 3/1962 Rogers 3 17-140 3,067,363 12/1962 Fleckenstein 317- 3,160,794 12/1964 Gill 3 l7155.5 X

LEE T. HIX, Primary Examiner- 

